Population genetics

2) Mutation

-Change in the DNA sequence -Less important in the short term because multiple generations pass before allele appears at noticeable frequency

4) Genetic Drift

-Genetic drift occurs when the number of reproducing individuals in a population is too small to ensure that all the alleles in the gene pool will be passed on to the next generation in their existing frequencies. -Genetic drift may result in one allele becoming fixed and one allele disappearing in a population.

3) Natural Selection

-If individuals of all genotypes are subject to natural selection and do not have equal rates of survival and reproductive success, allele frequencies may change from one generation to the next. -Natural selection is the principal force that shifts allele frequencies within large populations.

5) Migration

-Migration occurs when individuals move between the populations. -It may have a large effect on allele frequency if the rate of migration is large or if the allele frequency of the migrant population differs greatly from that of the population to which it is moving.

Hardy-Weinburg mathematical definitions for Allele and Genotypic frequencies:

1) Allele Frequencies = p (A) + q (a) = 1 2) Genotypic Frequencies = (p + q) 2 = p2 (AA) + 2pq (2Aa) + q2 (aa) = 1

6 factors (evolutionary forces) that can disrupt equilibrium:

1) Non-random mating 2) Mutation 3) Selection 4) Random genetic drift: small populations easily disrupted 5) Migration 6) Meiotic drive: one allele recovered more frequently than other

Under the ideal conditions, what 2 predictions does the Hardy-Weinberg model make?

1) The frequencies of the alleles in the gene pool do not change over time. 2) If 2 alleles at a locus, A and a, are considered, then after one generation of random mating the frequencies of genotypes AA:Aa:aa in the population can be calculated as: p^2 + 2pq+q^2= 1 (p=frequency of allele A and q+ frequency of allele a)

5 assumptions about the theoretical population described by the Hard-Weinberg law:

1) There is no selection; individuals of all genotypes have equal rates of survival and equal reproductive success. 2) No mutation. No new alleles are created or converted from one allele into another by mutation 3) No migration. Individuals do not migrate into or out of the population. 4) size; the population is infinitely large. (aka the population is large enough that sampling errors and other random effects are negligible). 5) Individuals in the population mate randomly.

3 important consequences of Hardy-Weinberg law:

1) it shows that dominant traits do not necessarily increase from one generation to the next. 2) that genetic variability can be maintained in a population since, once established in an ideal population, allele frequencies remain unchanged. 3) if we invoke hardy-weinberg assumptions, then knowing the frequency of just one genotype enables us to calculate the frequencies of all other genotypes at that locus.

neutral genes from Hardy-weinberg

Application of the hardy-Weinberg model can also reveal "neutral genes" in a population gene pool-- those not being operated on by the forces

Hardy-Weinburg law assumes what things?

Law assumes random mating each generation and no disruption of allele frequencies or genotypic frequencies.

Allele Frequency

Measurement of the proportion of a particular allele of all alleles for a single gene present in the population gene pool.

Non random mating

Non random mating, does not, by itself, alter allele frequencies, but by altering genotype frequencies, it indirectly affects the course of evolution.

1) Non-random mating (3 forms)

Nonrandom mating can take the form of: 1) positive assortive mating in which similar genotypes are more likely to mate than dissimilar ones. 2) negative assortive mating in which dissimilar genotypes are more likely to mate than similar ones. 3) inbreeding in which mating individuals are related.

Hardy-Weinberg theory can be used to predict?

The frequencies of carriers for disease genes in populations.

Gene pool

The total of all alleles possessed by reproductive members of a population

Hardy-Weinburg law

They demonstrated that in natural populations an equilibrium is reached at which the frequencies of different alleles of a gene remain constant through time if not disturbed. p = frequency of the dominant allele q = frequency of the recessive allele

Population

local group of individuals belonging to the same species, which are actually or potentially interbreeding

Genotypic frequency

measurement of the proportion of individuals in a population having a particular genotype (e.g. AA, Aa, or aa).

6) Meiotic drive/gamete selection

process which causes some alleles to be over-represented in the gametes e.g. alleles that favor or disfavor gamete viability

Population genetics

the study of genetic variation in populations and how it changes over time.